1. Field of the Invention
The present invention relates to a stator structure, and more particularly to a stator structure for a direct-current fan motor.
2. Description of the Prior Art
A conventional direct-current fan motor basically comprises a stator structure, a rotor structure, and a frame. There has been developed in recent years a kind of compact direct-current fan motor used in combination with semi-conductors, eliminating the use of the frame and minimizing the size of the stator and rotor structures to achieve size reduction.
According to the working principle of direct-current fan motors, the stator structure is employed to control a circuit board to cause a coil to generate intermittent connection. Therefore, there form an alternating field on the magnetic pole. The alternating field may be regarded as a rotating magnetic field. The inter-repulsion between the alternating field and the magnetic field generated by an annular rubber magnet on the rotor structure drives the rotor.
As for the conventional stator structure of direct-current fan motors, there are different coil winding methods, which can be divided into two main types. In the first type, the coil is wound along the external diameter of the spindle of the stator structure; then magnetic plates are provided on both sides of the coil. However, although this method makes coil winding relatively convenient, the polar area of the magnetic pole is relatively small. Relatively, the magnetic flux is also small, so that the electromechanical characteristics are relatively poor. In the second type, silicon steel sheets are punched to form integrally magnetic plates in a radial shape. The method of winding is along gaps between magnetic poles, and the coil is wound around the yoke of the magnetic pole. However, although the polar area of the magnetic pole is relatively large, and there is relatively more magnetic flux, since the gaps between adjacent magnetic poles are narrow, the distribution of coil windings is not uniform. Besides, during winding, the lead wire is likely to be cut by sharp edges of the magnetic poles, resulting in high wire cutting rates. Consequently, the rate of faulty products is also high.